diff options
| author | Hugh Dickins <hugh@veritas.com> | 2005-10-29 18:16:08 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@g5.osdl.org> | 2005-10-29 21:40:38 -0700 |
| commit | 7ee78232501ea9de2b6c8f10d32c9a0fee541357 (patch) | |
| tree | 2041a36a13bdd8b096dfbf52b63a87739ea97d6b /kernel/fork.c | |
| parent | fd3e42fcc888a773572282575d2fdbf5cfd6216e (diff) | |
| download | lwn-7ee78232501ea9de2b6c8f10d32c9a0fee541357.tar.gz lwn-7ee78232501ea9de2b6c8f10d32c9a0fee541357.zip | |
[PATCH] mm: dup_mmap down new mmap_sem
One anomaly remains from when Andrea rationalized the responsibilities of
mmap_sem and page_table_lock: in dup_mmap we add vmas to the child holding its
page_table_lock, but not the mmap_sem which normally guards the vma list and
rbtree. Which could be an issue for unuse_mm: though since it just walks down
the list (today with page_table_lock, tomorrow not), it's probably okay. Will
need a memory barrier? Oh, keep it simple, Nick and I agreed, no harm in
taking child's mmap_sem here.
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'kernel/fork.c')
| -rw-r--r-- | kernel/fork.c | 9 |
1 files changed, 4 insertions, 5 deletions
diff --git a/kernel/fork.c b/kernel/fork.c index 0e7fe4a8a8df..2a587b3224e3 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -192,6 +192,8 @@ static inline int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) down_write(&oldmm->mmap_sem); flush_cache_mm(oldmm); + down_write(&mm->mmap_sem); + mm->locked_vm = 0; mm->mmap = NULL; mm->mmap_cache = NULL; @@ -251,10 +253,7 @@ static inline int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) } /* - * Link in the new vma and copy the page table entries: - * link in first so that swapoff can see swap entries. - * Note that, exceptionally, here the vma is inserted - * without holding mm->mmap_sem. + * Link in the new vma and copy the page table entries. */ spin_lock(&mm->page_table_lock); *pprev = tmp; @@ -275,8 +274,8 @@ static inline int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) goto out; } retval = 0; - out: + up_write(&mm->mmap_sem); flush_tlb_mm(oldmm); up_write(&oldmm->mmap_sem); return retval; |